Wolgarston High School confirmed the case in a letter to parents on November 4, and said the school would be unable to provide hot food for students until November 16.
The letter says: "I am writing to inform you that we have been informed that a member of staff has received a positive test result for Covid-19 and are therefore self-isolating for 10 days.
"We have been working closely with Public Health England who have advised that individuals who have been in close contact with the member of staff should also self-isolate for 14 days as a precaution.
"For information, the member of staff has had no close contact with any students.
"Unfortunately, we will be unable to provide hot food for students until Monday 16th November and I apologise in advance for the inconvenience.
"Students need to bring a packed lunch including a refillable water bottle during this period. The canteen and hall will remain open at break and lunch times as an eating area.
"Students who receive a free school meal or wish to purchase a cold drink or snack will only be able to do so at lunchtime. There is a very limited supply of cold refreshments.
"I appreciate this news will undoubtedly give rise to anxiety or concerns.
"Please rest assured that we are taking every precaution to ensure the safety and wellbeing of our students, staff and the wider community, including enhanced cleaning routines, social distancing and ensuring good hand and respiratory hygiene."